The present invention concerns a regulable hydraulic dashpot for motor vehicles. The dashpot has a shock-absorbing piston and a shock-absorbing cylinder. The piston travels into and out of the cylinder on a rod. It divides the cylinder into two hydraulics compartments. The piston accommodates constrictions that incorporate pressure-sensitive valves. The piston also has at least one bypass port. A system of electromagnetically controlled valves reroutes the bypass ports in accordance with whether the dashpot is in the suction state or the compression phase.
A dashpot of this genus is known from German Application P 4 216 987. The bypass is rerouted by two electromagnetically operated valves. Each pressure-sensitive valve communicates in parallel or in series with an electromagnetically controlled bolt. The electromagnetically controlled bolts travel into and out of a bore. Such a dashpot allows graduated regulation of absorption in both the suction and compression phase in accordance with four performance parameters.
Another dashpot is known from German OS 3 835 705 A1. The level of absorption can be varied force-proportionally independent of the piston's speed. The piston accommodates for this purpose two isolated valves. The second valve accommodates a fluid reservoir. The level of pressure exerted on the plunger in the second valve by the fluid in the reservoir can be varied by the first valve, which is electromagnetically controlled. The base line, however, is difficult to establish when the electromagnet is off. Another drawback is that valves that are required to generate such a high level of absorption so often react slowly if at all due to the time needed to establish pressure in the reservoir.